US3725619A

US3725619A - Electric disconnect switch having improved counter balance mechanism

Info

Publication number: US3725619A
Application number: US00246006A
Authority: US
Inventors: Kinnon J Mc
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1972-04-20
Filing date: 1972-04-20
Publication date: 1973-04-03
Anticipated expiration: 1990-04-03

Abstract

An electric disconnect switch comprising a switch blade movable between an open and closed position with respect to a relatively stationary contact means and a counterbalance mechanism to assist in moving the switch blade between the open and closed position.

Description

United States Patent 1 [111 3,725,619

McKinnon 1 Apr. 3, 1973 [541 ELECTRIC DISCONNECT SWITCH 56 l W 'iikf'erii'c'bs CF66 m HAVING IMPROVED COUNTER UNITED STATES PATENTS BALANCE MECHANISM 3,079,474 2/1963 Beach et al. ..200/48 A [76] Inventor: John P. McKinnon, Monroeville,

P Primary Examiner-Herman J. Hohauser Attorney-A T. Stratton et a1. [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

221 l iled: #5611372 [21] Appl.No.: 246,006

" [57] ABSTRACT An electric disconnect switch comprising a switch blade movable between an open and closed position with respect to a relatively stationary contact means [52] U.S. Cl. ..200/48 A an a nt r alan m chanism to assist in moving 51 m. Cl. ..H0lh 31/00 e switch blade e n the open and closed posi- [58] Field of Search.200/48 R, 48 A; 200/48 R, 48 A tionf v 4 Claims, 5 Drawing Figures PATENTEDAFR3 I973 ,725,519

SHEET 1 [IF 2 H6 117 IOO- COUNTER-BALANCE MOMENT (MAIN SPRING ONLY) so-- E 701- E 1 g 60" i 5 35 i i SWITCH BLADE MOMENT O. 1 I I 5 a z i g 2O E ll9 r I 9o 60 so 0 CLOSED OPEN DEGREES TRAVELED FROM VERTICAL 3 PATENTEUAPR3 I975 SHEET 2 0F 2 ELECTRIC DISCONNECT SWITCH HAVING IMPROVED COUNTER BALANCE MECHANISM BACKGROUND OF THE INVENTION This invention relates to large electrical disconnect switches and more particularly to the counterbalance mechanism which forms a part of such switches.

Generally the pivotal type of disconnect switch includes a blade having one end pivotally attached to a fixed support mounted on a stationary insulator stack and having the other end adapted for swinging motion about the pivot to a point between the spaced jaws of fixed contacts mounted upon another insulating stack; whereupon, rotation of the blade about its longitudinal axis provides high pressure engagement with the fixed contact jaws. When the switch is to be opened, the blade is first axially rotated to effect disconnection between the jaws and the blade and thereafter the blade is swung to the fully opened position. To effect closing of the disconnect switch, the blade is swung between the jaws and thereafter axially rotated to effeet high pressure contact between the blade and the fixed contacts. In the large pivotal blade type of outdoor high voltage electric switch there is a problem in providing easy movement of the switch blade between the open and closed position. Large pivotal blade type switches have extremely large switch blade moments which require a counterbalancing mechanism in order to reduce the effort required to open and close the switch. A counterbalance mechanism as disclosed in detail in U.S. Pat. No. 3,079,474 issued Feb. 26, 1963 to E. F. Beach et al. and which is assigned to the same assignee as the present application can be used effectively on large pivotal blade type switch to reduce the effort required to open and close the switch. Ideally,

the counterbalance spring effort should just match the switch blade moment at all portions of travel so that only friction losses need be supplied by the operator. Practically, however, the spring characteristics only approximate the switch blade moment as the switch is opened or closed. It is the usual practice to plot both switch blade moment and spring moment on graph paper and to adjust both initial and final spring tension to produce the minimum differential in moment between the two curves. This method is effective in minimizing the amount of force required to operate the switch; however, there is considerably mismatch between the spring moment and the switch blade moment, where the switch is almost open or almost closed. When the switch is mounted in the horizontal position, operating force is required to push down the switch blade until it is approximately l from the closed position at which time it falls rapidly under its own weight into contact with the fixed contact jaw. If the switch is rapidly closed, the switch blade at about 80 from the open position suddenly falls and hits into the fixed contact jaw stopping quickly. This sudden stop can result in bending of the switch blade or mechanical damage to the switch.

SUMMARY OF THE INVENTION In accordance with the invention, an electric switch comprising a switch blade having one end movable into and out of engagement with an associated relatively stationary contact means is provided with a counterbalance mechanism which closely matches the inertia of the switch blade movement. The switch blade has secured to the other end a generally tubular electrically conducting crank member which is rotatably supported on an electrically conducting hinge member. The counterbalancing mechanism is attached to a crank member in order to assist in moving the switch blade from the horizontal closed position to the vertical open position. The force of the improved counterbalance mechanism closely matches the switch blade moment even at the extreme opening or closing area. The improved counterbalancing mechanism comprises a large coil spring, compressible to oppose the weight of the blade when in positions other than the vertical, a helper spring, which works after the switch blade is passed, approximately from thevertical, to prevent the switch-blade from falling into the contact jaw with great force and an opposing spring which works between approximately 0 to 10 to assist in the initial movement of the switch blade when going from the open to the closed position. The helper and the opposing springs help the counterbalance mechanism to closely match the switch blade moment, and to eliminate any mismatch near the ends of the permitted switch blade travel.

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages of the invention will be apparent from the following detail description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is, a view in side elevation of a disconnecting switch structure embodying the principal features of the invention;

FIG. 2 is a top plan view of the switch structure shown in FIG. 1;

FIG. 3 is a graph showing the switch blade moment .and the main coil spring moment adjusted to produce minimum differential in moment between the two curves;

FIG. 4 is an enlarged partial elevation view taken partly in section of the disconnect switch of FIG. I in the closed position; and

FIG. 5 is a view of a portion of FIG. 4 showing the switch blade in the opened position.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings and FIGS. 1 and 2 in particular, there is shown a disconnecting switch assembly 10 which comprises three spaced

insulator stacks

32, 34 and 36 which are normally mounted upon a common metal base support 33 as disclosed in detail in U.S. Pat. No. 3,079,474 issued Feb. 26, 1963 to E.F. Beach et al. and which is assigned to the same assignee as the present application. Each of the insulator stacks 32, 34 and 36 comprises a plurality of insulators which are preferably formed from porcelain or similar insulating materials. The number of insulators required in each of the

insulator stacks

32, 34 and 36 depends upon the operating voltage of the electrical system for which the disconnecting switch 10 is supplied. Insulator stacks 32 and 34 may be mounted upon fixed pedestals or spacers 35 which in turn may be secured to the top of the associated base 33 which may be a metal channel in configuration. As described in the above-mentioned U.S. Pat. No. 3,079,474 the insulator stack 36 is mounted upon a shaft 17. The lower end of the shaft 17 is rotatably mounted in a bearing 18 which is secured to the associated base 33. As is indicated in FIGS. 1 and 2, an operating level 37 may be secured to the shaft 17 provided at the lower end of the insulator stack 36, to rotate the insulator stack 36. The operating lever 37 is adapted for connection to any conventional means for operating the operator lever 37 to effect rotation of the associated shaft 17 and the insulator stack 36 about its own longitudinal axis. In order to positively connect the operating lever 37 and the associated rotatably insulator stack 36 to the balance of the operating mechanism of the disconnecting switch 10, as will be described in greater detail hereinafter, a shaft 112 is secured to a flange member 113 which in turn is secured to the top of the insulator stack 36. The shaft 112 extends upward from the upper end of the insulator stack 36 to thus form an extension of the shaft 17, which is provided at the lower end of the insulator stack 36 to which the operating lever 37 is attached. The shaft 112 passes through an opening provided in a terminal end casting 1 10, which is substantially aligned with the axis of rotation of the shaft 112 and the associated insulator stack 36, and has mounted at the upper end thereof a crank arm 100, which is rotatable with the shaft 112. The crank arm 100 extends generally transversely with respect to the axis of rotation of the shaft 112. In order to facilitate rotation of the shaft 112, inside the opening provided in the terminal end member 110, one or more bearings may be disposed inside the opening provided in the terminal end member 110. It is to be noted that in a particular application the crank arm 100 may be formed integral with the shaft 112.

As illustrated in FIGS. 1 and 2 the disconnecting switch includes a generally U-shaped relatively stationary contact assembly 40 which is mounted on and secured to the top of insulator stack 32. The stationary contact assembly 40 includes a pair of spaced contact jaws 43 which are of the reverse loop type, well known in the art, and having the characteristic of magnetically increasing contact pressure on switch blade 50 and of forcing the switch blade 50 downward between the contact jaws 43 in a direction against the blade stop 73, in response to momentary high current. The contact jaws 43 may be composed of zirconium copper which when heat treated combines very high conductivity with excellent spring characteristics. The resilient nature of the zirconium copper eliminates the need for additional spring means to bias the jaws 43 toward each other for gripping the switch blade 50. The contact jaws 43 are rigidly attached to the insulator 32 by any suitable means such as bolting. A terminal pad 72 is rigidly attached to the contact jaws 43 by a suitable means such as welding or brazing. The blade stop 73 may be formed integral with the terminal pad 72.

In order to provide an electrically conducting path between the stationary contact assembly 40 and the electrically conducting parts of the disconnecting switch 10 which are mounted on top of the insulator stack 34, when the disconnect switch 10 is in a closed condition as shown in FIGS. 1 and 2, the movable switch blade 50 is provided. The switch blade 50 is elongated in shape and included a main body or central portion 56 which is generally tubular in configuration and which is formed from an electrically conducting material such as copper, a copper alloy or aluminum.

The blade 50 also includes an end portion or beaver tail member 53 at its left end which is generally rectangular in cross section, to provide high pressure contact areas which are adapted to engage the contact jaws 43 of the stationary contact assembly 40. The end portion 53 of the switch blade 50 may be formed integrally with the associate main body portion 56 or may be formed as a separate piece which is secured to the left end of the main body portion 56 by suitable means.

In order to support the switch blade 50 for rotation about its own axis and for arcuate movement about an axis, which extends generally perpendicularly with respect to the longitudinal axis of the switch blade 50, the right end of the main body portion 56 of the switch blade 50 is secured to the left end of a hinge support casting 48 for movement therewith. The switch blade 50 is mounted for axial rotation within a pair of spaced aligned

bearings

46 and 47. The bearing 47 is mounted upon a hinge casting 48 and the bearing 46 is mounted upon a hinge casting extension 49. The hinge casting extension 49 is fixedly attached to and spaced from the hinge casting 48 by means of a pair of substantially parallel integral bridge members 51. A switch blade crank arm 42 is carried between the

bearings

46 and 47 in abutting relationship therewith so that operation of the crank arm 42 provides free rotation of the blade 50 about its longitudinal axis, but prevents any longitudinal motion of the switch blade 50 with respect to the hinge casting 48. The hinge casting 48 is rotatably supported by a pair of hinge pins 19 which are fixed in opposite sides of the hinge casting 48 and extends through the sides of the casting 48.

In order to support the hinge casting member 48 for rotation about an axis, which is generally perpendicular with respect to the longitudinal axis of the switch blade 50, and to support the switch blade 50 which is assembled on the hinge member 48, for arcuate movement about the axis, spaced arms 82 of the hinge support member are disposed on opposite sides of the hinge member 48, as best shown in FIG. 2. The hinge support casting 48 is pivotally supported between the arms 82 of the hinge support member 80 by the electrically conducting hinge pins or studs 19 which pass through substantially aligned openings provided in the arms 82 and the hinge support casting 48. The heads of the hinge pins 19 are secured to the arms 82 of the support frame 80 by suitable means. A continuous current path is established between the contact assembly 40 and hinge support member 80 by suitable means well known in the art such as described in detail in U.S. Pat. No. 3,079,474 issued Feb. 26, l963 to E.F. Beach et al., U.S. Pat. No. 3,194,905 issued July 13, 1965 to F.W. Jewell et al., or U.S. Pat. No. 3,500,006, issued Mar. 10, 1970 to E.W. Kuhn. In order to provide a continuous current path from the hinge support member 80 to the terminal end casting 110, a tubular conducting" member 79 is provided. The tubular conducting member 79 also serves as a housing for counterbalancing mechanism 60 hereinafter described in detail.

With the switch blade 50 in the closed position the free end 53 is in high pressure contact with the contact jaws 43 of the fixed contact 40, and the toggle mechanism comprised of link 29, slip joint 6, bolt 26, ball 25, socket 27 and crank arm is in an over toggle position, as illustrated in FIG. 2. The over toggle position of the toggle mechanism, when the switch is closed, positions the flattened end of the blade 50 in full engagement with the fixed contact jaws 43. When the crank arm 100 is rotated counterclockwise, as viewed from the top in FIG. 2, the toggle mechanism moves through the dead center position to effect opening of the disconnect switch 10.

When the toggle mechanism is in the initial over toggle position the nut 133 in slip joint 6 is nearly abutting the end of the link 29, but is spaced slightly from the end of link 29 allowing the switch blade 50 to rest upon the stop. 73. As the toggle mechanism moves through the dead center position the bolt 26 is permitted to slide longitudinally within the

bores

28 and 30 to effectively shorten the link 29 to permit the toggle mechanism to pass through the dead center position. At the dead center position the nut 133 abuts the end of the link 29 as shown in cross section of FIG. 4.

Further rotation of the arm 100 toward the under toggle position from the dead center position effects a lengthening of link 29 through the operation of slip joint 6 wherein bolt 26 slides longitudinally in

bores

28 and 30 until adjusting nut 133 abuts the end of extension 31. It is seen that the lengthening of link 29 through the operation of slip joint 6 eliminate any longitudinal pull on the link 29 as arm 100 rotates, but transmits the lateral force applied by arm 100 to bolt 26 so that the link provides a lateral force on the crank 42 to thus rotate the switch blade 50, in hinge member 48, to effect disconnection between switch blade 50 and the contact jaws 43.

Thereafter continued movement of the arm 100 carries nut 133 into engagement with the inner end of link extension 31 thus preventing further lengthening of the link 29 so that continued movement of the crank arm 100 provides a longitudinal pull on the link 29, which force is transmitted through the pin 39 and the crank 42 to swing the switch blade 50 and hinge member 48 about pivot pins 19 until the blade is in a substantially vertical position.

To close the disconnect switch 10, the arm 100 is moved in a clockwise direction, this swings the blade 50 between the contact jaws 43 where the switch blade 50 rests upon the switch blade stop 73. Thereafter further rotation of the arm 100 effects movement of the toggle linkage through dead center to the over toggle position whereupon the extension of slip joint 6 occurs so that the flat end of the switch blade 50 is thus rotated into engagement with the fixed contact jaws 43 while the blade rests on the stop 73.

In order to assist the operating crank arm 100 in moving the switch blade 50 from the horizontal closed position to the vertical open position, there is provided the previously mentioned counterbalancing mechanism 60 comprised of a main coil spring 99' compressible to oppose weight of the switch blade 50 when the switch blade 50 is in positions other than the vertical. The main coil spring 99 is positioned within the tubular conductor 79 and extends longitudinally inthe tube 79, with one end of the spring 99 abutting the end of the tubular member 79 away from the hinge casting 48, and where the other end abuts the spring guide member 98 positioned across the tube and operable for movement along the length of the tube. Three rollers 101 of which only one is shown are fastened at 120 intervals around the edge of the guide member 98 by any suitable means and are operable to engage the inner periphery of the tube 79 so as to prevent binding between the guide member 98 and the inner wall of the tube 79 when the guide member 98 travels the length of the tube during the operation of the disconnect switch 10. The force of the main coil spring 99 is transmitted to the hinge casting 48 by means of a link 102 pivotally attached at one end by a suitable pin means 103 to the central portion of the guide member 98 and pivotally attached at the other end of the hinge casting 48 by means of a pin 104 extending through a suitable aperture in a spaced flanged member .105, extending rearward and external of hinge casting 48.

In the counterbalancing mechanism 60 the force of the spring multiplied by the lever arm as defined by the distance between pin 104 and hinge pins 19 is approximately equal to the gravitational force on the blade 50 and other parts which tend to move the hinge casting 48 counterclockwise about the pivot pin axis defined by pins 19. Large high voltage disconnect switches 10 have extremely large switch blades 50 which have a large moment requiring a strong counterbalance mechanism 60 in order to reduce the effort required to open and close the switch 10. The switch blade 50 moment is approximately equal to a constant multiplied by the sine of the angle between the switch blade 50 position and its fully open position, which is approximately 90 from the horizontal. Ideally, the main counterbalance spring 99 characteristic should just match the switch blade moment at all positions of travel so that only friction losses need be supplied by the operator. In practical application, however, the spring 99 works through a changing effective radius multiplied by a compression stroke which depends on the sine of an angle which has a slight phase shift from the switch blade 50 angle. As shown in FIG. 3, it is the usual prac tice to plot both the switch blade 50 moment and the main spring 99 moment and adjust both initial and final spring tension to produce the minimum differential in moment between the two curves. When the main spring 99 moment is less then the switch blade 50 moment the counterbalancing force is insufficient to support the blade 50 and the blade 50 tends to fall unless restrained.

Areas

116 and 118 represent portions of switch blade 50 travel where the switch blade 50 moment exceeds the main spring 99 moment and the blade 50 tends to fall. When the main spring 99 moment is greater than the switch blade 50 moment, the switch blade 50 tends to rise unless restrained.

Areas

117 and 119 represent portions of switch blade 50 travel where the main spring 99 moment exceeds the switch blade 50 moment and the switch blade 50 tends to rise. Of particular interest is the small negative moment area 116 between approximately to As the large switch blade 50 is closed during the portion of travel between approximately 45 to 80 it must be forced down, at approximately 80 the main spring 99 moment becomes less than the switch blade 50 moment and the damage to the disconnect switch 10. To help alleviate I this difficulty with counterbalance mechanism 60,

which comprises a spring means 99 that is operable for the full travel of the switch blade 50, a helper spring 96 which works between approximately 80 to 90 is added to the counterbalance mechanism 60. This helper spring 96 can be quite small when compared to the main spring 99. The area 116 between the curve of the main spring 99 moment and the curve of the switch blade 50 moment represents the work which the helper spring must do in order to make the counterbalance 60 moment just match the switch blade 50 moment between 80 to 90. The volume of the helper spring 96 is approximately proportional to the work it must do, and as can be seen, this is quite small compared to the work done by the main spring 99. With the helper spring 96 added to the counterbalance mechanism 60 it will be necessary to force the switch blade 50 from about 45 until the switch blade 50 is in a completely closed position.

An opposing spring 97, similar to the helper spring 96 but opposing the main spring 99, can be introduced to operate at the opening end of the stroke to eliminate the excessive positive spring moment 119 present between about 8 to This would reduce the force required to open the disconnect switch 10.

Physically, the helper spring 96 would be mounted inside the main conducting tubular member 79 and would operate only during the final closing movement of the switch 10 between approximately 80 to 90 from the vertical open position. The opposing spring 97 would be mounted inside the main tubular conducting member 79 and would operate only during the initial closing movement of the switch 10 from approximately 0 to 10 from the vertical open position. With the helper spring 96 and the opposing spring 97 in place the moment of the counterbalancing mechanism 60 will better approximate the switch blade 50 moment, and the mismatch between the counterbalancing 60 moment and the switch blade 50 moment in area 116 and area 119 are eliminated. With the helper spring 96 in place, there will be a gradual slowing down of switch blade 50 and very nominal shock when the switch blade 50 contacts the switch blade stop 73 and the contact jaws 43.

Since numerous changes may be made in the above described apparatus and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description and shown in the accompanying drawings shall be 'interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An electrical switch comprising a relatively stationary contact member, an elongated switch blade having one end movable between engaged and disengaged positions with respect to said stationary contact member, an electrical conducting hinge casting secured to the other end of said switch blade for movement therewith, an electrically conducting end support member to support said hinge casting for rotation about an axis perpendicular to the longitudinal axis of said switch blade, a switch blade operating mechanism connected to said switch blade for pivotally moving said switch blade about a fixed pivot point between engaged and disengaged positions with respect to said stationary contact member, a tubular conducting member rigidly attached to said end support member, counterbalancing means for opposing the weight of the switch blade in the various positions around said fixed'pivot point, said counterbalancing means comprising a main coil spring and a helper means which aids said main coil spring during a portion of said switch operation, said main coil spring being mounted internally of said tubular conductor and having one end of said spring abutting one end of said tubular conductor, a linking means connecting the other end of said main spring and extending outward of said tubular conductor through the other end thereof and connected in pivotal relationship with said switch blade operating mechanism, one end of said helper means abutting one end of said tubular conductor and the other end of said helper means abutting said linking means during a small portion of the operating sequence.

2. The combination as claimed in claim 1 including an opposing means mounted inside said tubular electrical conductor to oppose the main spring during a portion of the switch operating sequence.

3. The combination as claimed in claim 1 wherein said helper means comprises a coil spring.

4. The combination as claimed in claim 2 wherein said opposing means comprises a coil spring.

Claims

1. An electrical switch comprising a relatively stationary contact member, an elongated switch blade having one end movable between engaged and disengaged positions with respect to said stationary contact member, an electrical conducting hinge casting secured to the other end of said Switch blade for movement therewith, an electrically conducting end support member to support said hinge casting for rotation about an axis perpendicular to the longitudinal axis of said switch blade, a switch blade operating mechanism connected to said switch blade for pivotally moving said switch blade about a fixed pivot point between engaged and disengaged positions with respect to said stationary contact member, a tubular conducting member rigidly attached to said end support member, counterbalancing means for opposing the weight of the switch blade in the various positions around said fixed pivot point, said counterbalancing means comprising a main coil spring and a helper means which aids said main coil spring during a portion of said switch operation, said main coil spring being mounted internally of said tubular conductor and having one end of said spring abutting one end of said tubular conductor, a linking means connecting the other end of said main spring and extending outward of said tubular conductor through the other end thereof and connected in pivotal relationship with said switch blade operating mechanism, one end of said helper means abutting one end of said tubular conductor and the other end of said helper means abutting said linking means during a small portion of the operating sequence.